Micro-fluidics relates to a multidisciplinary field comprising physics, chemistry, engineering and biotechnology that studies the behavior of fluids at volumes thousands of times smaller than a common droplet. Micro-fluidic components form the basis of so-called “lab-on-a-chip” devices or biochip networks that can process micro-liter and nano-liter volumes of fluid and conduct highly sensitive analytical measurements. The fabrication techniques used to construct micro-fluidic devices are relatively inexpensive and allow mass production of highly elaborate, multiplexed devices. In a manner similar to that for microelectronics, micro-fluidic technologies enable the fabrication of highly integrated devices for performing several different functions on the same substrate chip.
Micro-fluidic chips are becoming a key foundation to many of today's fast-growing biotechnologies, such as rapid DNA separation and sizing, cell manipulation, cell sorting and molecule detection. Micro-fluidic chip-based technologies offer many advantages over their traditional macro-sized counterparts. Micro-fluidics is a critical component in, amongst others, gene chip and protein chip development efforts.
In all micro-fluidic devices, there is a basic need for controlling the fluid flow, that is, fluids must be transported, mixed, separated and directed through a micro-channel system consisting of channels with a typical width of about 0.1 mm. A challenge in micro-fluidic actuation is to design a compact and reliable micro-fluidic system for regulating or manipulating the flow of complex fluids of variable composition, e.g. saliva and full blood, in micro-channels. Various actuation mechanisms have been developed and are at present used, such as, for example, pressure-driven schemes, micro-fabricated mechanical valves and pumps, inkjet-type pumps, electro-kinetically controlled flows and surface-acoustic waves.
U.S. Pat. No. 4,846,715 discloses a voice coil motor assembly for a voice coil motor printwheel setting apparatus comprising a plate having the voice coil motor coils mounted thereon. The plate is adapted for attachment to a printed circuit board by pins electrically connected to the voice coils. Picker links having coil magnets connected thereto are stacked in sequence and the final assembly is completed by enshrouding the voice magnets with the voice coils mounted on the plate. For driving an assembly of voice coil motor's there is a voice coil matrix switching device. Switching is performed by power transistors.
WO 2006/035938 discloses an oscillation magnetic field generation device including an electromagnet and an electromagnet drive circuit for driving the electromagnet. Excitation current is supplied from a DC power source to the electromagnet. The electromagnet drive circuit includes: a switching element for controlling on/off of the excitation current; an electromagnetic energy emission circuit and pulse generator means.
WO 00/47983 discloses an electrochemical biosensor system based on enzyme-linked immuno-magnetic sandwich assay wherein an interdigitated array of electrodes is equipped with a magnet to attract magnetic beads. The magnetic field generation device 150 may be activated/deactivated by an on/off switch 152, or the like. The switch may be under the control of a system controller 100 or the like.
US 2006/020371 A1 discloses a microfluid system (300) containing fluid in proximity to complementary metal oxide semiconductor (CMOS) fabricated field-generating components (200). At least one controller controls the field-generating components to generate an electric or magnetic field sufficiently strong as to interact with at least one sample suspended in the fluid. FIG. 15 illustrates the contents of the microcoil switching unit 460-4 shown in FIG. 14. Each microcoil switching unit includes a microcoil 212 connected to a current direction (polarity) switch 460-5 (S1) and a coil enable switch 460-6 (S2).
US 2004/077105 discloses an array of microcoils. The microcoils are fabricated from conductive traces. FIGS. 10-11 show the principle of addressing individual micro-electromagnetic units by using electric switches. In FIG. 10, each unit 41 is connected to the common electrical current source 43 and the common ground 45 (i.e. current sink) through two electric switches 37 and 239 in series. The switch 37 is controlled by electric signals applied to the rows 30 of the electroconductive lines. The switch 39 is controlled by electric signals applied to the columns of the electroconductive lines.
US 2004/0070557 discloses an active matrix display device. To compensate for the threshold voltage which tends to cause luminance irregularities easily, a threshold compensation pixel circuit is used.